Here is the full list of all 30 The Legend of Korra achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Completed the game on Extreme difficulty.
Completed the highest difficulty of Pro-bending.
Won a Face-Off in a Pro-bending match.
Collected every treasure item.
Purchased 12 talismans.
Went into Avatar State 10 times.
Collected 10 cabbages.
Maxed out all bending types.
Obtained all combos.
Spirit-bended 200 dark spirits.
Got 10 Knockouts in Pro-bending matches.
Countered 100 times.
Performed 100 Finishing Moves.
Completed Chapter 8.
Used your first equipped item.
Completed all tutorials.
Completed Chapter 7.
Dodged 100 times.
Completed a Naga Running sequence without hitting anything.
Completed Chapter 6.
Completed Chapter 5.
Completed Chapter 4.
Went into Clash Mode 10 times.
Jumped 100 times.
Completed Chapter 3.
Entered the Collection Screen for the first time after finding a treasure.
Equip your first item in Korra's Room.
Bought your first item at the shop.
Completed Chapter 2.
Completed Chapter 1.